The present invention relates generally to methods and apparatus for use in making electrical interconnections and, more particularly, to such methods and apparatus that are utilized in conjunction with making crimped connections involving at least one magnet wire lead of an inductive device such as a dynamoelectric machine.
In the manufacture of dynamoelectric machines, the excitation windings or coils are usually made of magnet wire-- i.e., copper or aluminum wire covered with a suitable layer of insulation. It has been known for some time that it is generally less expensive to use a crimp connection approach (as opposed to brazing, welding, or soldering) when interconnecting leads or taps from such coils with one or more other wires (e.g., other magnet wire segments or stranded lead wires). It has also been determined, however, that for some of the more demanding applications it is difficult and expensive (although technically possible) to provide crimped interconnections which will retain suitable conductivity characteristics over a long period of time.
For example, in hermetically sealed refrigerating compressor applications, stator assemblies (including excitation windings and electrical interconnections therewith) are normally exposed to a refrigerant fluid such as, e.g., one of the freon refrigerant materials. In this type of application, an internal failure (e.g., a high resistance connection) usually will require that the sealed compressor be replaced. Accordingly, it is necessary that any crimped interconnection be of very high quality and have a long life expectancy (in the neighborhood of twenty years, for some applications).
The need for crimped connections is especially great for hermetically sealed refrigeration motors with aluminum windings because the magnet wire insulation used for motors of this type creates a practically unsolvable problem when making connections by welding or brazing.
Experience has now shown that reliable connections may be made, but that it is important to control the final height of a crimped interconnection as a function of the cross-sectional area or size of the conductor (or other material) contained within the crimped connector. The optimum crimped connector height varies (as will be understood by persons skilled in the art) from one connector to another, for a given conductor area or size. Thus, it has previously been found to be desirable to provide methods and apparatus for varying the final crimped connector height and for feeding a "stuffer wire," when needed, to a crimping station.
In one prior approach devised by another, a pneumatically operated toggle linkage has been provided, wherein a generally "L" shaped arm has been supported at one extremity thereof by an eccentric pin. The other extremity of the arm has been connected to a frame supported ram; and the central portion of the arm has been connected (at a pivot) to one end of another arm. The second end of the another arm then has been interconnected with crimping tooling which was constrained to move along a path toward and away from other crimping tool parts.
In the approach just described, the eccentric pin has been interconnected with a crank arm which, in turn, was connected to a pneumatic cylinder. Then, upon closure of a foot pedal switch by an operator, the pneumatic cylinder could be energized to rotate the eccentric pin from a first rotational position to a second rotational position. The two different rotational positions of the eccentric pin provided two different "effective toggle stroke lengths," and thus have been utilized to provide two different finished crimped connector heights.
When following the approach just described, a stator assembly has been placed in a stator holder, moved to a crimping station, and rotated until a winding lead has been adjacent to the crimping station. It then has been necessary for the operator to mentally determine whether or not the crimp height controlling foot pedal should be depressed.
One variation from the above has been to provide "stuffer" wire feeding apparatus. Again, when such apparatus has been used, it has been necessary for an operator to decide whether stuffer wire should or should not be included in a crimped interconnection.
The above described approaches have not been fully satisfactory for a number of reasons. For example, the methods utilized have relied upon accurate operator recognition of the need for a particular one of two different crimp heights; and accurate operator recognition of whether or not a stuffer wire segment needed to be used. Moreover, in the case of apparatus with which I am familiar, the eccentric pin has been adjustable to only two different discrete positions with the result that the difference between a maximum crimp height and minimum crimp height has always been the same, even though it might be desired to vary such difference.
In crimp connection making apparatus, bits and pieces of wire, connectors, and foreign particles tend to appear and accumulate around a crimping station. It will be understood that it would also be desirable to provide methods and apparatus for removing such pieces and particles.
I have now also determined that connections not having desirable characteristics may be produced as a result of stuffer wire misplacement within a crimped connector having magnet wire therein. As used herein, "magnet wire" indicates electrically insulated copper, aluminum, aluminum alloy, or any other electrically insulated conductive material used in the manufacture of motors, generators, alternators, or transformers wherein electrical insulation of the conductive material is established and maintained by a thin, adherent, film-like coating on the conductive material. This coating, sometimes referred to as "varnish", adheres tenaciously to the conductive material, and is very tough yet flexible thereby to prevent cracking or crazing thereof during coil winding, coil placing, and coil shaping operations.
Because of the nature of the insulative coating on magnet wire, connectors having a multiplicity of serrations have been used. During a crimped-connection making process, the teeth or serrations of the connector clips are intended to pierce the magnet wire insulative coating and establish a low resistance interconnection between two or more magnet wire segments. In practice however, I have found that such interconnection may not be established if stuffer wire material is adjacent to the serrated surface of a clip while it is being crimped. This result seems to occur because the stuffer wire tends to fill the notches or grooves adjacent to the teeth of the clip, and inadequate penetration of the magnet wire insulation results.
It is an object of the present invention to provide new and improved methods and apparatus for removing scrap particles from the vicinity of the crimping station of crimp connection apparatus.